Climate Through Human History

Human Evolution and Climate

Roughly 13 million years ago, several centuries of drought caused East African forest to thin out.

The drier climate forced tree-dwelling primates out of their forest homes, challenging them to find new ecological niches in the advancing savannah.

Those primates that stayed became chimps, gorillas and a recently discovered intermediate species. Those that moved out became us.

About 4.5 million years ago Ramidus lived in Ethiopia with human and simian characteristics -- Ramidus may have been the first bipedal primate and was about 4 ft tall.

About 3.5 million years ago, upright walking had developed in East Africa - refashioning childbirth (babies born immature) and freeing up fore limbs for other tasks (they developed asymmetric capabilities, along with the brain).

By 3 million years ago, the brain of Australopithecus showed pronounced asymmetry, the larger left side handling manipulative abilities.

First primitive tools have been related to finds in Ethiopia - 2.6 million years old. Now tools used by Homo Habilis could supplant evolution as the main source of change.

Habilis to Sapiens

Tools made it possible and desirable to hunt in groups and to build shelters. The cooperative hunting would encouraged abilities including speed, accuracy and communication.

Habilis evolved and spread through and out of Africa. By 2 million years ago, Homo Erectus, five foot tall, was living in the cooler East Africa hill country, running down prey, searching for food and using specialized tools for butchering, pounding vegetables, cracking and sharpening animal bones.

By 600,000 years ago (brain size had doubled again) fire was in use, teeth were smaller, changes to the larynx and tongue allowed speech to develop.

About 120,000 years ago, Homo Sapiens moved out of East Africa into the Sahara, living complex lives in rock shelters. They hunted and gathered with tool kits and ranged over large distances. By 90,000 years ago they were in the Middle East. 40,000 years ago they had spread across Europe, traveling 200 miles per year. By 15,000 years ago they had crossed the Bering Straits into America, using tools to fashion warm clothes. Main races had differentiated, art forms developed.

Agricultural Revolution

About 12,000 years ago, there were about 5 million humans on Earth, living in hunting groups of about 25, very aware of and dependent on natural cycles. It took 15 square miles to support each hunter gatherer.

People then started to settle more or less permanently in appropriate places. Dry farming generated a food surplus, leading to an economy that could support specialities other than food production - only 3 square miles per settler were needed for food. The first villages were on the plains of the Levant, in view of the Mediterranean, a place fertile with plentiful fish and fruit. This region no longer contains its once vast primordial forests.

Around 7000 years ago, increasingly long spells of dry weather drove some riverine communities to invent irrigation in river valleys. This watershed event led to great food surpluses, increased population density, leaders and bureaucracies to measure and control the surplus. Trading began.

Writing developed as a way to keep track of property. Kingship was invented and the first cities were founded in Mesopotamia. Slash and burn techniques were used to clear forests. Animals were domesticated.

Time-line: the past 100,000 years of human existence and explores specific climate events which may have challenged or changed human activities.

Past 100,000 Years	End of Pleistocene
100,000 B.P.	Early Homo sapiens diet includes fish and seafood
90,000 B.P.	Recent discoveries in caves along South African coast dating to 70,000 years before present suggest people using bone tools and living on fish and mammals in the region.
80,000 B.P.
70,000 B.P.
60,000 B.P.
50,000 B.P.	Large scale extinctions of mammals and birds in Australia
40,000 B.P.	Cave paintings, stone and bone tools in much of Europe
30,000 B.P.	Cro-Magnons thrive in cold European climate... but not for long.
20,000 B.P.	Global temperature averages 14 degrees F cooler than today.
10,000 B.P.	Estimated 5 million Homo Sapiens on planet. Megafauna extinctions in North America

Additional Links

Human Evolution and Climate PDF presentation.

Climate Time Line Information Tool .